Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$78.39	9.280%	$85.6646	$85.66	$85.65	$85.70
Purchase #2	$152.27	10.264%	$167.899	$167.90	$167.90	$167.90
Purchase #3	$214.97	12.842%	$242.5764	$242.58	$242.60	$242.60
Purchase #4	$186.47	7.238%	$199.9667	$199.97	$199.95	$200.00
Purchase #5	$231.95	10.542%	$256.4022	$256.40	$256.40	$256.40
Purchase #6	$146.30	11.358%	$162.9168	$162.92	$162.90	$162.90
Purchase #7	$24.31	4.664%	$25.4438	$25.44	$25.45	$25.40
7 purchase totals =	$1,034.66		$1,140.8695	$1,140.87	$1,140.85	$1,140.90